Modification of fibrinogen chains during synthesis: glycosylation of B beta and gamma chains.

Specific immunoprecipitation and affinity chromatography on Con A-Sepharose of in vitro translated products derived from rat liver messenger ribonucleic acid (mRNA), total polysomes, and rough microsomes have been used to determine temporal events of glycosylation of the subunits of fibrinogen. The A alpha chain is not glycosylated, whereas both the B beta and the gamma chains have carbohydrate clusters (probably Asn linked). Evidence presented here shows that the gamma chain receives its core carbohydrate as an early cotranslational event. The B beta chain is glycosylated later and likely is glycosylated at the time of polypeptide termination or shortly after it is released from the ribosome into the cisternal space of the rough endoplasmic reticulum.